Auto-focus apparatus applied to image reading apparatus and the like

Abstract

In an auto-focus apparatus of the invention, an image sensor (e.g., a CCD) produces an image signal corresponding to an image on a microfilm. The image signal from the image sensor is encoded to a binary image signal by a binary encoding circuit. Alternation points (i.e., leading or trailing edges) of the binary image signal are counted by a counter. A system controller fetches count values from the counter, and detects an image position corresponding to a maximum count value. The system controller causes a lens driving circuit to move an imaging lens to the detected image position.

What is claimed is: 
     
       1. An auto-focus apparatus comprising: exposure means for exposing an image recorded on a film;   scanning means for scanning the image on a line by line basis and producing binary image signals representing the image;   optical means for projecting image light from the film exposed with said exposure means onto said scanning means;   setting means for setting a scanning position of said scanning means so as to scan a predetermined line in the image;   counting means for counting the number of times there is a transition of the binary image signals produced from said scanning means when it scans the predetermined line; and   focusing means for focusing said optical means so that a count value of said counting means satisfies a predetermined condition.   
     
     
       2. An apparatus according to claim 1, wherein said focusing means focuses said optical means so that the count value of said count means is at a maximum value. 
     
     
       3. An auto-focus apparatus comprising: scanning means for scanning an image on a line by line basis and producing binary image signals representing the image;   optical means for projecting the image onto said scanning means:   counting means for counting the number of times there is a transition of the binary image signals produced from said scanning means;   detection means for detecting an image line of the image with which a count value of said counting means satisfies a predetermined condition; and   focusing means for focusing said optical means based on the image signals obtained upon scanning by said scanning means of the image line detected by said detection means.   
     
     
       4. An apparatus according to claim 3, wherein said detection means detects the image line corresponding to a maximum count value of said counting means. 
     
     
       5. An apparatus according to claim 3, wherein said detection means detects the image line corresponding to a count value of said counting means which is larger than a predetermined value. 
     
     
       6. An apparatus according to claim 3, wherein said focusing means focuses said optical means so that the count value of said counting means satisfies a predetermined condition. 
     
     
       7. An apparatus according to claim 6, wherein said focusing means focuses said optical means so that the count value of said count means is at a maximum value. 
     
     
       8. An apparatus according to claim 3, wherein said optical means projects the image recorded on a film onto said scanning means. 
     
     
       9. An auto-focusing comprising: scanning means for scanning an image on a line by line basis and producing binary image signals representing the image;   optical means for projecting the image onto said scanning means;   moving means for moving a scanning position of said scanning means;   detection means for detecting a position of scanning by said scanning means with which the image signals from said scanning means satisfy a predetermined condition; and   focusing means for focusing said optical means based on the image signals obtained upon scanning by said scanning means of an image line of the scanning position detected by said detection means.   
     
     
       10. An apparatus according to claim 9, further comprising counting means for counting the number of times there is a transition of the binary image signals produced from said scanning scanning means, and wherein said detection means detects a scanning position with which a count value of said counting means satisfies a predetermined condition. 
     
     
       11. An apparatus according to claim 9, further comprising counting means for counting the number of times there is a transition of the binary image signals produced from said scanning means, and wherein said focusing means focuses said optical means so that a count value of said counting means satisfies a predetermined condition 
     
     
       12. An apparatus according to claim 9, wherein said optical means projects the image recorded on a film onto said scanning means. 
     
     
       13. An auto-focus apparatus comprising: scanning means for scanning an image and producing image signals representing the image;   optical means for projecting the image onto said scanning means;   focusing means for focusing said optical means based on the image signals from said scanning means; and   inhibiting means for inhibiting focusing by said focusing means when the image signal from said scanning means is not in a predetermined state.   
     
     
       14. An apparatus according to claim 13, further comprising means for displaying a message indicating that the focusing is inhibited by said inhibiting means. 
     
     
       15. An apparatus according to claim 13, wherein said optical means allows manual focusing. 
     
     
       16. An apparatus according to claim 13, wherein said focusing means comprises counting means for counting the number of times there is a transition of the image signals produced from said scanning means, and wherein said focusing means focuses said optical means so that a count value of said counting means satisfies a predetermined condition. 
     
     
       17. An apparatus according to claim 16, wherein said inhibiting means inhibits the focusing when the count value of said counting means is below a predetermined value. 
     
     
       18. An apparatus according to claim 13, wherein said optical means projects the image recorded on a film onto said scanning means. 
     
     
       19. An auto-focus apparatus comprising: scanning means for scanning an image and producing image signals representing the image;   optical means for projecting an image onto said scanning means;   setting means for setting a reference value so that the image signals from said scanning means satisfy a predetermined condition;   comparison means for comparing the image signals from said scanning means with the reference value set by said setting means to convert the image signals into binary image signals; and   focusing means for focusing said optical means so that the binary image signals from said comparison means satisfy a predetermined condition.   
     
     
       20. An apparatus according to claim 19, wherein said setting means comprises counting means for counting the number of times there is a transition of the image signals from said scanning means, and sets the reference value so that a count value of said counting means satisfies a predetermined condition. 
     
     
       21. An apparatus according to claim 19, wherein said setting means selects any one of a plurality of predetermined reference values. 
     
     
       22. An apparatus according to claim 19, wherein said focusing means focuses said optical means so that the number of times there is a transition of the binary image signals satisfies a predetermined condition. 
     
     
       23. An apparatus according to claim 14, wherein said optical means projects the image recorded on a film onto said scanning means. 
     
     
       24. An auto-focus apparatus comprising: sensor means for producing an output in accordance with incident light;   optical means for projecting an image onto said sensor means;   determining means for determining a focus position of said optical means based on the output of said sensor means; and   focusing means for focusing said optical means based on at least two focus positions determined by said determining means.   
     
     
       25. An apparatus according to claim 24, wherein the at least two focus positions are determined by said determining means with respect to different image positions. 
     
     
       26. An apparatus according to claim 24, wherein said focusing means focuses said optical means based an average value of at least two focus positions determined by said determining means. 
     
     
       27. An apparatus according to claim 24, wherein said optical means projects the image recorded on a film onto said sensor means. 
     
     
       28. An apparatus according to claim 24, further comprising scanning means for scanning the image projected by said optical means and producing image signals representing the image. 
     
     
       29. An apparatus according to claim 24, wherein the at least two focus positions are obtained by means of performing a plural number of times the operation for determination of the focus position by said determining means. 
     
     
       30. An apparatus according to claim 1, wherein said setting means searches the predetermined line with which the image signals from said scanning means satisfy the predetermined condition. 
     
     
       31. An apparatus according to claim 1, wherein a focusing operation of said focusing means is inhibited when a count value of said counting means is below a predetermined value. 
     
     
       32. An apparatus according to claim 1, wherein a focusing scanning means has a line sensor comprising a plurality of photo-electric conversion elements arranged in a line configuration. 
     
     
       33. An apparatus according to claim 3, wherein a focusing operation of said focusing means is inhibited if said detection means does not detect an image line with which a count value of said counting means satisfies the predetermined condition. 
     
     
       34. An apparatus according to claim 3, wherein said scanning means has a line sensor comprising a plurality of photo-electric conversion elements arranged in a line configuration. 
     
     
       35. An apparatus according to claim 11, wherein said focusing means focuses said optical means so that the count value of said count means is at a maximum value. 
     
     
       36. An apparatus according to claim 9, wherein said scanning means has a line sensor comprising a plurality of photo-electric conversion elements arranged in a line configuration, and said moving means moves said line sensor. 
     
     
       37. An apparatus according to claim 16, wherein said focusing means focuses said optical means so that the count value of said counting means is at a maximum value. 
     
     
       38. An apparatus according to claim 16, wherein said counting means counts the number of times there is a transition of the image signals obtained upon scanning different lines of the image with said scanning means. 
     
     
       39. An apparatus according to claim 20, wherein said setting means sets the reference value so that a count value of said counting means is at a maximum value. 
     
     
       40. An apparatus according to claim 20, wherein said setting means sets the reference value so that a difference between a count value of said counting means in a case of in-focus and that in a case of defocus is a maximum value. 
     
     
       41. An apparatus according to claim 22, wherein said focusing means focuses said optical means so that the number of times there is a transition of the binary image signals is a maximum value. 
     
     
       42. An apparatus according to claim 22, wherein said scanning means has a line sensor comprising a plurality of photo-electric conversion elements arranged in a line configuration. 
     
     
       43. An auto-focus apparatus for image reader comprising: exposure means for exposing an image recorded on a film;   scanning means for scanning an image and producing image signals representing the image;   optical means for projecting image light from the film exposed by said exposure means;   determining means for determining a focus position of said optical means based on the image signals from said scanning means; and   focusing means for focusing said optical means based on the focus position determined by said determining means.   
     
     
       44. An apparatus according to claim 43, wherein said determining means determines the focus position based on the number of times there is a transition of the image signals. 
     
     
       45. An apparatus according to claim 43, wherein said scanning means has a line sensor comprising a plurality of photo-electric conversion elements arranged in a line configuration. 
     
     
       46. An apparatus according to claim 43, further comprising moving means for moving a scanning position by said scanning means.